1. Field of the Invention
This invention relates to a fault diagnostic apparatus and, more particularly, to a fault diagnostic apparatus for an electric appliance such as an air conditioning system.
2. Description of the Prior Art
A presently known heat pump type air conditioning system has the ability to determine when the air conditioning system is operating improperly and has provisions for indicating to the owner of the system when service is required and also for indicating to the serviceman the general nature of the fault or faults involved in the improper operation.
Such a fault diagnostic apparatus for a serviceman is disclosed, for example, in U.S. Pat. No. 4,381,549. The fault diagnostic apparatus of this patent can indicate a plurality of fault items in a fixed specified order in a fault diagnostic operation mode. The fault items are displayed by code numbers corresponding to each possible fault item on a light emitting diode (LED) matrix display for visual readout of information data. The fault diagnostic apparatus of the patent, however, has a drawback in that a plurality of LEDs is required for the LED matrix display. The fault diagnostic apparatus of this patent also has another drawback in that the serviceman cannot immediately inquire about specific fault item, or examine the fault items in any desired order. Further, the fault diagnostic apparatus of this patent has an important drawback in that the serviceman easily may misread the code number because many numbers are displayed for short intervals.